In the 2000 U.S. Census, 35 million Americans over 65 years of age were counted, representing 12.4% of the U.S. population. Approximately 30% of those over age 65 in the U.S. have a significant hearing loss that is sufficient to make them hearing-aid candidates. Yet, only about 20% of those who could benefit from hearing aids actually seek them out and, of those who do seek them out, only about 40-60% are satisfied with them and use their hearing aids regularly. Nonetheless, those over 60 years of age still represent the largest group of hearing-aid purchasers in the U.S., with those over age 60 purchasing about 2/3 of the hearing aids sold. Thus, understanding the factors that determine hearing-aid benefit and developing means to improve benefit are significant issues for many older adults in the U.S. The most common communication complaint of older adults with impaired hearing is that they can hear speech, but can't understand it. This is especially true when there are competing sounds, typically other speech, in the background. Hearing aids, to be effective, must address this common complaint and improve speech understanding, especially in backgrounds of competing speech. Hearing aids have the potential to improve speech communication by restoring the audibility of previously inaudible speech sounds, typically high-frequency speech sounds for older adults, but this potential does not appear to be realized. In the proposed project, we intend to examine further the aided speech-understanding performance of older adults in backgrounds of competing speech. The contributions of central and cognitive factors to the performance of older adults in these situations represent the focus of a series of laboratory experiments. Experiments address the ability of older listeners to use sound-segregation cues to selectively attend to the message from one talker while ignoring competing messages from other talkers. Additional experiments assess whether it is the fluctuating nature of the competing speech stimulus, the semantic/syntactic structure of the competing speech stimulus, or both, that underlie the difficulties experienced by older adults. Finally, another experiment examines the ability of older adults to reconstruct the speech message from the temporal, spectral, and spectro-temporal fragments heard in noise. The most common communication complaint of older adults with impaired hearing is that they can hear speech, but can't understand it, especially when there are competing sounds, typically other speech, in the background. Hearing aids, to be effective for older adults, must address this common complaint and improve speech understanding. In the proposed project, we intend to examine further the factors impacting the aided speech- understanding performance of older adults in backgrounds of competing speech.